The described invention relates generally to systems and methods for sealing ring terminals and other types of terminals used in the automotive industry and other industries, and more specifically to sealing systems and methods that include heat shrink tubing and sealant systems that are used in combination with the heat shrink tubing. The heat shrink tubing systems can be single-layered systems or multi-layered systems and the sealant systems may include hot melt adhesives, butyl mastics, or other types of sealants.
Ring terminals are typically used to attach electrical wires to studs or posts (such as those found on vehicle batteries and other batteries) and are manufactured in various types and sizes. Ring terminals typically include a ring portion and a wire attachment/connection portion to which electrical wires are connected by welding or other means. Non-insulated ring terminals can be crimped or soldered and may be finished off with heat shrink tubing to insulate and protect the connection formed between the electrical wires and the wire attachment portion of the terminal. Heat shrink tubing (HST) is a shrinkable plastic tube often used to insulate electrical wires. HST provides abrasion resistance and environmental sealing protection for stranded and solid wire conductors, connections, joints, and terminals used in various electrical applications. HST can also be used to repair damaged insulation on electrical wires, bundle wires together, and to create cable entry seals. As stated above, HST may be a single-walled system or a multi-walled system, wherein the multi-walled system includes at least one heat-shrinkable layer and at least one layer of a sealant system. Heat shrink tubing is commonly manufactured from fluoropolymer or polyolefin, which shrinks radially when heated. The process of shrinking an HST is referred to as “recovering” an HST and the predetermined temperature at which a HST starts to recover is referred to as its “recovery temperature”. As an HST recovers, i.e., shrinks, it exerts an inward force against the items it surrounds, which is referred to as the “hoop stress” of the HST. More specifically, hoop stress (also known as cylinder stress) is the force exerted circumferentially (perpendicular both to the axis and to the radius of the object) in both directions on every particle in the tubing or cylinder wall. The degree of hoop stress is determined by certain HST characteristics such as the type of base material, wall thickness, degree of cross-linking, and degree of expansion. Hoop stress is also affected by process parameters such as temperature of recovery and degree of recovery.
Ring terminals currently used with passenger and commercial vehicle electrical systems include single-wire and multi-wire configurations. Multi-wire configurations have created significant challenges with regard to sealing the terminal-wire interface area on such terminals. External sealant systems that include the use of heat shrink tubing and an adhesive/sealant layer have been previously used to create a water tight seal in between and outside of the electrical wires attached to the terminal. However, existing sealant systems are not capable of sealing the multiple electrical wires (e.g., six or more wires) included in multi-wire configurations in a simple and reliable manner. A first problematic situation involves the wicking of water (if present in the operating environment) from the ring portion of the terminal onto the wire attachment portion of the terminal, then onto the attached electrical wires, and then from one end of the electrical wires to the other end thereof through the welded or crimped interface. A second problematic issue involves the flow or oozing of excessive adhesive or sealant onto the ring portion of the ring terminal. Adhesive that is present on the ring portion can interfere with the metal to metal contact that is needed for an effective electrical contact.
To overcome the limitations of sealing systems that involve the use of external adhesive and heat shrink tubing, the industrial approach currently used involves a multi-component, multi-step process. This process is labor intensive and expensive; therefore, there is an ongoing need for a sealing system for use with ring terminals that meets all functional requirements in a simplistic, reliable, and cost-effective manner.